Ambient Power-Enabled Internet of Things: 3GPP Physical Layer Standardization Overview

Zero-energy devices, also known as Ambient power-enabled Internet of Things (A-IoT) devices, rely on harvesting ambient energy to operate. These self-sustainable devices do not need manual battery recharging or replacement, making them easy to maintain. A-IoT can address new Internet of Things (IoT) use cases within the cellular ecosystem which the existing cellular IoT technologies were not designed for. To address these use cases, a technical study was conducted by the Third Generation Partnership Project (3GPP) in Release 19 to identify the challenges and develop solutions for a new cellular radio access technology for A-IoT devices that can be deployed in 5G New Radio (NR) spectrum using or coexisting with existing NR network infrastructure. The key challenges for cellular A-IoT devices include low power budget, intermittent energy availability, limited synchronization and computational capabilities due to simplified hardware, and coexistence with NR. In this paper, the 3GPP standardization work on A-IoT is reviewed, with a focus on the physical layer aspects considered in the aforementioned Release 19 study. First, the nomenclature for A-IoT device types, architectures, and deployment scenarios is summarized. This is complemented by a description of the A-IoT physical layer design for downlink and uplink, including aspects such as physical channels, waveform, modulation, coding, preamble, and multiple access. The issues related to coexistence of A-IoT and NR are also outlined. A brief discussion on the upcoming 3GPP A-IoT standardization work concludes the paper.